Piston for material dispensing gun cartridge



F- J. KRIEPS April 16, 1968 PISTON FOR MATERIAL DISPENSING GUN CARTRIDGEFiled Feb. 3, 1966 frzuen or: Fran/ JKrzqypJ United States Patent 01fice 3,378,175 Patented Apr. 16, 1968 3,378,175 PISTON FOR MATERIALDISPENSING GUN CARTRIDGE Frank J. Kricps, Elmhurst, Ill., assignor toContainer Corporation of America, Chicago, III., a corporation ofDelaware Filed Feb. 3, 1966, Ser. No. 524,691 3 Claims. (Cl. 222-327)This invention relates to dispensing guns of the type used to dispenseviscous materials such as caulking compounds and greases from expendablecartridges, and more particularly to an improved piston for anexpandable cartridge.

As is known to those familiar with the art, heavy or viscous materialssuch as caulking compounds and greases are packed in expendable orthrow-away cartridges which have a dispensing spout on one end thereofand a movable piston on the other end thereof which may be engaged by aplunger of a dispensing gun and moved forward to force the material tobe dispensed through the cartridge and out of the dispensing member.

One problem frequently incurred in connection with the operation ofmaterial dispensing guns, when used to dispense relatively viscousmaterials, is that many of these materials have an elasticity whichcauses the material to continue to flow out of the dispensing spoutafter the movement of the plunger and piston has been stopped. This isbecause the material has been under compression, and, even though themovement of the piston has stopped,

the material is still under some degree of compression and tends toexpand, with the result that the least resistance is offered by thedispensing spout so that material can continue to flow out for a shortperiod of time.

In the past attempts have been made to produce dispensing gun cartridgeswith features designed to overcome the continued dispensing or flow ofthe material. Many types of so-called stop flow pistons have beenproduced which include a central flexible membrane or diaphragm which issupposed to flex axially forwardly and rearwardly to overcome thisproblem. An example of this type of arrangement can be found in US.Letters Patent No. 2,833,451 wherein the membrane of the cartridgepiston is supposed to be deflected forwardly of the forward most pointof the piston side walls by the plunger as the plunger is moved forward,and then is supposed to flex rearwardly when the piston is withdrawn.Although this arrangement would appear in theory to overcome theproblem, in actual practice many times the diaphragm will fail to returnto its relaxed or rearward-most position and will remain in the forwardmost position so that the desired effect is never accomplished.

It is therefore a primary object of this invention to provide, in adispensing gun cartridge of the type described, an improved pistondesigned to prevent or minimize the flow of material out of thecartridge dispensing spout after the dispensing gun plunger has beenreleased.

A more specific object of the invention is the provision, in adispensing gun cartridge of the type described, of improved unitarypiston having a cylindrical outer wall presenting internal rearwardlyfacing abutment surfaces, a round central section, and an annular frontwall interconnecting the outer and the central section and adapted toafford a spring-like action for the central section to permit it to moveforward when engaged by the plunger, but whose forward movement islimited by the engagement between the plunger and the abutment surfacesof the outer wall, so that the central section cannot move forwardbeyond the forward edge of the outer wall, and which can move rearwardlywhen pressure on plunger is released so as to suck the materialrearwardly and prevent it from continuing to flow out of the cartridgespout.

These and other objects of the invention will be apparent from anexamination of the following description and drawings, wherein:

FIGURE 1 is a side elevational view of a material dispensing gun andcartridge of the type to which this invention is related;

FIGURE 2 is an enlarged view of part of the structure in FIGURE 1, withportions of the structure shown in vertical cross section to illustratethe relationship of the gun plunger to a cartridge piston which embodiesfeatures of the invention. In this view the piston is shown in itsrelaxed position before being actuated by the gun plunger;

FIGURE 3 is a view similar to FIGURE 2 but showing the piston in thecompletely engaged or depressed position with the central section of thepiston being shown in its forwardmost position;

FIGURE 4 is an end elevational view of the piston which is illustratedin FIGURE 2.

It will be understood that, for purposes of clarity, cer tain elementshave been intentionally omitted from certain views where they areillustrated to better advantage in other views.

Referring now to the drawing for a better understanding of theinvention, and more particularly to FIGURE 1, it will be seen that amaterial dispensing gun, indicated generally at G and provided with amovable piston P, is illustrated holding an expendable tubularcartridge, indicated generally at C, of the type used in the packagingof relatively viscous materials such as grease or caulking compound.

Cartridge C, as best seen in FIGURES 1 and 2, is of cylindrical shapehaving a cylindrical. outer wall 16, defining a tube for holding thematerial M, and which has its forward end closed by a conventionaldispensing spout number 12 and its rearward end closed by a pistonmember, indicated generally at 14, embodying features of the invention.

In actual practice the tube is formed with dispensing spout member 12affixed to the forward end thereof, and then, after the tube has beenfilled with the material to be packaged, piston member 14 is inserted inthe opposite end of the tube to close the tube. In operation, after thecartridge has been placed within a caulking gun in the position shown inFIGURE 1, as the trigger of the gun is depressed the plunger is urgedforward into an engagement with the piston member 14. As piston member14 is moved forward by the plunger it compresses the material in thetube and drives it forward in the tube and out through dispensing spoutmember 12.

Turning now to FIGURE 2 of the drawing; it Will be seen that pistonmember 14 is a one-piece 0r unitary article which is preferably moldedfrom a relatively stiff, though resilient, plastic material such apolypropylene. Piston member 14 includes a generally cylindrical outerwall 16 and a preferably round central section 20 which areinterconnected by an annular front wall 18.

Central section 20 includes a preferably cylindrical inner wall 22 whichis disposed concentrically within outer Wall 16, but is of appreciablyless length than outer wall 16, so that when the piston is in thenon-engaged or relaxed condition the front and rear edges of the pistonouter wall extend forwardly and rearwardly, respectively of centralsection inner wall 22. The area defined by inner wall 22 is closed by adome-like center wall 24 which, at its outer periphery, is formedintegrally with the rear edge of inner wall 22. Center wall 24 is bowedforwardly so as to prevent a convex surface on its front side and aconcave surface on its rear side.

Still referring to FIGURE 2, it will be seen that front wall 18 isintegrally formed at its outer edge with the front edge of outer wall 16and is integrally formed at its inner edge with the front edge of innerwall 22. Front wall 18 slopes radially inwardly and axially rearwardlyfrom the front edge of outer wall 16, as best seen in FIGURE 2, when thepiston member is in its relaxed condition, so that central section 20 ofthe piston is disposed rearwardly of the forward extremity of the pistonouter wall 16.

As best seen in FIGURES 2 and 4, outer wall 16 is provided on its insidewith a plurality of integrally formed, circumferentially spaced,longitudinally extending, internal ribs which present rearwardly facingabutment surfaces 32 disposed in common plane extending in a directionnormal to the axis of the piston and lying between the rearwardextremity of the central section, when the piston is in relaxedcondition, and the forward extremity of the outer wall 16.

The purpose of the ribs and abutment surfaces is to take the ultimate orbasic force from the thrust of the plunger and transmit it to the pistonouter wall 16 after the central section of the piston has been initiallyengaged by the piston in its forward movement. When the plunger of thegun moves forward to engage the piston member it first contacts therearward edges of central section inner wall 22 and moves the centralsection forward, or to the left as seen in FIGURE 2. Because of the snugfrictional engagement between the piston outer wall and the side wall ofthe cartridge, the piston member itself does not move forward until theplunger has deflected the central section forwardly a sufficientdistance to cause the outer edges of the plunger to engage the abutmentsurfaces of the piston member ribs as shown in FIGURE 3.

At this point the full thrust of the plunger force is transmitted to thepiston member outer wall through the rib surfaces, and the piston memberis thereafter driven forward in the cartridge thereby forcing thematerial fort wardly and out of the spout or dispensing member 12 of thecartridge.

Because of the angle of the rearwardly sloping front wall 18 a greatresiliency is imparted to the central section of the piston member, sothat when the pressure on the plunger of the gun is released the outerwall urges the central section to spring rearwardly. This takes thepressure off of the compressed material in the tube and allows a portionof it to move rearwardly and occupy the space in the area of the centralsection, so that it will not be under such pressure as to cause it toflow out of the dispensing spout of the cartridge.

The essence of the invention resides in the provision of the abutmentsurfaces on the outer wall ribs which carry the load of the plungerforce, so that the force does not have to be borne entirely by thecentral portion of the piston member. It has been found in arrangementswhere the central section of the piston member bears the entire load itpops forward of the front edges of the outer wall and does not have theforce or strength or resiliency to return to its original position toaccomplish the function intended, namely the preventing of flow ofmaterial out of the spout member after the plunger has been withdrawn.

In order to facilitate insertion of the piston member into the cartridgeat the time the cartridge is filled and closed, the forward edge ofouter wall 16 may be recessed slightly, as shown at 34. This not onlyfacilitates insertion of the piston member but it also facilitates theforward distention of the central section and front wall as it isengaged by the gun plunger.

I claim:

1. In an expendable tubular cartridge for a material dispensing gun witha movable plunger, which cartridge includes a cylindrical side wallforming a tube open at opposite ends and a dispensing spout memberfixedly associated with the front end of the tube remote from the gunplunger for closing said front tube end, a unitary piston memberslidably positioned within said tube at the rear end thereof adjacentsaid plunger for closing said rear tube end and for urging said materialthrough said tube toward said dispensing spout member when actuated bysaid gun plunger, said piston member being formed from a relative stiffthough resilient plastic material such as polypropylene and comprisingin combination:

(a) a cylindrical outer wall disposed in snug frictional engagement withthe inner surface of said cartridge side wall for slidable movementlongitudinally of the cartridge only when actuated by said plunger;

(b) a circular central section, including:

(i) a cylindrical inner wall concentrically disposed within the outerwall and being of lesser length than said outer wall;

(ii) a round center wall formed integrally with the rear edge of saidinner wall to close the center of the piston member and being bowedforwardly to present a convex surface on its front side and a concavesurface on its rear side;

(c) a flexible, annular, transverse, front wall having its outer edgeformed integrally with the front edge of said outer wall and extendingradially inwardly and rearwardly and having its inner edge formedintegrally with the front edge of said inner wall;

(d) a plurality of internal, circumferentially spaced, longitudinallyextending ribs presenting coplanar, rearwardly facing, abutment surfacesthe location of which relative to said central section, is such thatupon initial contact between the plunger and pistonmember the plungerwill first engage the central section and move it forward relative tothe outer wall, against the resilient pressure of said front wall andthe material in said tube, until the plunger engages said rib abutmentsurfaces to thereby prevent further forward movement of said centralsection beyond the front edge of said outer wall and further transmitthe driving force of the plunger through said ribs to said outer wall tocause said piston member to move forward in said tube;

(e) said front wall afiording a spring-like action for said centralsection to permit it to move forward when engaged by the plunger and tomove it rearwardly when pressure on the plunger is released to suck thematerial rearward and thereby prevent it from continuing to flow out ofthe cartridge through said spout member.

2. In an expendable tubular cartridge for a material dispensing gun witha movable plunger, which cartridge includes a cylindrical side wallforming a tube open at opposite ends and a dispensing spout memberfixedly associated with the front end of the tube remote from the gunplunger for closing said front tube end, a unitary piston memberslidably positioned within said tube at the rear end thereof adjacentsaid plunger for closing said rear tube end and for urging said materialthrough said tube toward said dispensing spout member when actuated bysaid gun plunger, said piston member comprising in combination:

(a) a cylindrical outer wall disposed in snug frictional engagement withthe inner surface of said cartridge side wall for slidable movementlongitudinally of the cartridge only when actuated by said plunger;

(b) a circular central section, including:

(i) a cylindrical inner wall concentrically disposed within the outerwall and being of lesser length than said outer wall;

(ii) a round center wall formed integrally with the rear edge of saidinner wall to close the center of the piston member and being bowedforwardly to present a convex surface on its front side and a concavesurface on its rear side;

(c) a flexible, annular, transverse, front wall having its outer edgeformed integrally with the front edge of said outer wall and extendingradially inwardly and rearwardly and having its inner edge formedintegrally with the front edge of said inner wall;

(d) said outer wall presenting at least one internal, rearwardly facing,abutment surface the location of which relative to said central section,is such that upon initial contact between the plunger and pistonmemberthe plunger will first engage the central section and move it forwardrelative to the outer wall, against the resilient pressure of said frontwall and the material in said tube, until the plunger engages saidabutment surface to thereby prevent further forward movement of saidcentral section beyond the front edge of said outer wall and further totransmit the driving force of the plunger to said outer wall to causesaid piston member to move forward in said tube;

(e) said front wall affording a spring-like action for said centralsection to permit it to move forward when engaged by the plunger and tomove it rearwardly when pressure on the plunger is released to suck thematerial rearward and thereby prevent it from continuing to flow out ofthe cartridge through said spout member.

3. In an expendable tubular cartridge for a material dispensing gun witha movable plunger, which cartridge includes a cylindrical side wallforming a tube open at opposite ends and a dispensing spout memberfixedly associated with the front end of the tube remote from the gunplunger for closing said front tube end, a unitary piston memberslidably positioned within said tube at the rear end thereof adjacentsaid plunger for closing said rear tube end and for urging said materialthrough said tube toward said dispensing spout member when actuated bysaid gun plunger, said piston member comprising in combination:

(a) a cylindrical outer wall disposed in snug frictional engagement withthe inner surface of said cartridge only when actuated by said plunger;

(b) a central section disposed within the outer wall;

(c) a flexible, annular, transverse, front wall having its outer edgeformed integrally with the front edge of said outer wall and extendingradially inwardly and rearwardly and having its inner edge formedintegrally with the front edge of said inner wall;

(d) said outer wall presenting at least one internal, rearwardly facing,abutment surface the location of which relative to said central section,is such that upon initial contact between the plunger and pistonmemberthe plunger will first engage the central section and move it forwardrelative to the outer wall, against the resilient pressure of said frontwall and the material in said tube, until the plunger engages saidabutment surface to thereby prevent further for- Ward movement of saidcentral section beyond the front edge of said outer wall and further totransmit the driving force of the plunger to said outer wall to causesaid piston member to move forward in said tube;

(c) said front wall affording a spring-like action for said centralsection to permit it to move forward when engaged by the plunger and tomove it rearwardly when pressure on the plunger is released to suck thematerial rearward and thereby prevent it from continuing to flow out ofthe cartridge through said spout member.

References Cited UNITED STATES PATENTS 2,833,451 5/1958 Sherbondy222-327 3,029,985 4/1962 Krueger et a1 222--327 3,250,443 5/1966 Abbott222327 ROBERT B. REEVES, Primary Examiner.

1. IN AN EXPENDABLE TUBULAR CARTRIDGE FOR A MATERIAL DISPENSING GUN WITHA MOVABLE PLUNGER, WHICH CARTRIDGE INCLUDES A CYLINDRICAL SIDE WALLFORMING A TUBE OPEN AT OPPOSITE ENDS AND A DISPENSING SPOUT MEMBERFIXEDLY ASSOCIATED WITH THE FRONT END OF THE TUBE REMOTE FROM THE GUNPLUNGER FOR CLOSING SAID FRONT TUBE END, A UNITARY PISTON MEMBERSLIDABLY POSITIONED WITHIN SAID TUBE AT THE REAR END THEREOF ADJACENTSAID PLUNGER FOR CLOSING SAID REAR TUBE END AND FOR URGING SAID MATERIALTHROUGH SAID TUBE TOWARD SAID DISPENSING SPOUT MEMBER WHEN ACTUATED BYSAID GUN PLUNGER, SAID PISTON MEMBER BEING FORMED FROM A RELATIVE STIFFTHOUGH RESILIENT PLASTIC MATERIAL SUCH AS POLYPROPYLENE AND COMPRISINGIN COMBINATON: (A) A CYLINDRICAL OUTER WALL DISPOSED IN SNUG FRICTIONALENGAGEMENT WITH THE INNER SURFACE OF SAID CARTRIDGE SIDE WALL FORSLIDABLE MOVEMENT LONGITUDINALLY OF THE CARTRIDGE ONLY WHEN ACTUATED BYSAID PLUNGER; (B) A CIRCULAR CENTRAL SECTION, INCLUDING: (I) ACYLINDRICAL INNER WALL CONCENTRICALLY DISPOSED WITHIN THE OUTER WALL ANDBEING OF LESSER LENGTH THAN SAID OUTER WALL; (II) A ROUND CENTER WALLFORMED INTEGRALLY WITH THE REAR EDGE OF SAID INNER WALL TO CLOSE THECENTER OF THE PISTON MEMBER AND BEING BOWED FORWARDLY TO PRESENT ACONVEX SURFACE ON ITS FRONT SIDE AND A CONCAVE SURFACE ON ITS REAR SIDE;(C) A FLEXIBLE, ANNULAR, TRANSVERSE, FRONT WALL HAVING ITS OUTER EDGEFORMED INTEGRALLY WITH THE FRONT EDGE OF SAID OUTER WALL AND EXTENDINGRADIALLY INWARDLY AND REARWARDLY AND HAVING ITS INNER EDGE FORMEDINTEGRALLY WITH THE FRONT EDGE OF SAID INNER WALL; (D) A PLURALITY OFINTERNAL, CIRCUMFERENTIALLY SPACED, LONGITUDINALLY EXTENDING RIBSPRESENTING COPLANAR, REARWARDLY FACING, ABUTMENT SURFACES THE LOCATIONOF WHICH RELATIVE TO SAID CENTRAL SECTION, IS SUCH THAT UPON INITIALCONTACT BETWEEN THE PLUNGER AND PISTONMEMBER THE PLUNGER WILL FIRSTENGAGE THE CENTRAL SECTION AND MOVE IT FORWARD RELATIVE TO THE OUTERWALL, AGAINST THE RESILIENT PRESSURE OF SAID FRONT WALL AND THE MATERIALIN SAID TUBE, UNTIL THE PLUNGER ENGAGES SAID RIB ABUTMENT SURFACES TOTHEREBY PREVENT FURTHER FORWARD MOVEMENT OF SAID CENTRAL SECTION BEYONDTHE FRONT EDGE OF SAID OUTER WALL AND FURTHER TRANSMIT THE DRIVING FORCEOF THE PLUNGER THROUGH SAID RIBS TO SAID OUTER WALL TO CAUSE SAID PISTONMEMBER TO MOVE FORWARD IN SAID TUBE; (E) SAID FRONT WALL AFFORDING ASPRING-LIKE ACTION FOR SAID CENTRAL SECTION TO PERMIT IT TO MOVE FORWARDWHEN ENGAGED BY THE PLUNGER AND TO MOVE IT REARWARDLY WHEN PRESSURE ONTHE PLUNGER IS RELEASED TO SUCK THE MATERIAL REARWARD AND THEREBYPREVENT IT FROM CONTINUING TO FLOW OUT OF THJE CARTRIDGE THROUGH SAIDSPOUT MEMBER.